Piglet Resuscitation from Asphyxia

The fractional inspired oxygen concentration (FiO₂) was decreased to 10% by adding nitrogen for 45 minutes. Nitrous oxide was continued during this period. Five minutes of room air (without nitrous oxide) was then supplied to briefly reoxygenate the heart. This brief reoxygenation period is required for successful cardiac resuscitation. The endotracheal tube was then occluded for 7 minutes to produce asphyxia. The piglets were resuscitated with 100% oxygen by mechanical ventilation, manual chest compressions, and epinephrine (100 mcg/kg, IV). Chest compressions were administered at a goal rate of 100 beats per minute and to attain goal mean arterial blood pressure (MAP) ≥40 mmHg. Animals that did not regain spontaneous circulation after 3 minutes of chest compressions were considered “failed to resuscitate.” After resuscitation, the FiO₂ was decreased to 30% to maintain oxyhemoglobin saturation > 93%, nitrous oxide and isoflurane were restarted, and sodium bicarbonate and calcium chloride were administered for metabolic acidosis and hypocalcemia. Sham-operated piglets received the same anesthesia, surgery, and duration of anesthesia, but without arrest. Their lungs were ventilated with FiO₂ 30% throughout the experiment.